View Single Post
Old 05-25-2011, 09:36 AM
BarelyAWake's Avatar
BarelyAWake BarelyAWake is offline
Motorized Bicycle Elite Member
Join Date: Jul 2009
Location: Maine
Posts: 7,212
Default Re: Anyone out there with a "BoosBottle Industries" Expansion Chamber??

There's far more than aesthetics to be considered with an expansion chamber, everything about exhaust system is important, not least of which is the headpipe diameter and length... which the above product doesn't seem to consider at all.

Originally Posted by Junster View Post
Remember how the pipe works. The exhaust sound wave expands down the front taper then hits the rear taper (which is usually at double the angle of the front) reflecting the wave back at the header tube. The idea is to get the header length "tuned" to have the wave hit the exhaust port just before the piston closes it. Stuffing some of the energy back into the port along with some of the exhaust gases as the piston goes up. The faster the engine is spinning (or the shorter the piston stroke is) the shorter the header needs to be to deliver the charge at the right time. To long a header and it's late, to short and it's early. A little long and you get a broader band. As they get shorter the rpm range is more sensitive but the pipe adds more to the HP. It's a balancing act.
some links;
A two-stroke

Reply With Quote